1. Field of Invention
The methods and apparatuses of the present invention are to be used in providing systems for cool thermal storage and/or water purification. The methods are based on solid-liquid-vapor multiple phase transformation operations for conducting direct contact in-situ crystal formation during a charging period and for conducting direct contact in-situ crystal melting operations during a discharging period. Chilled water is produced by coupling a water chilling operation with a crystal melting operation. The applications of the methods and apparatuses may be extended to non-aqueous systems.
The current market for cool thermal storage is created by electric utilities. The benefits derived by the utility may include increased revenue, lower cost production, or shifting summer demand. Electric utilities supplement persuasive marketing programs with attractive utility rates to sell the thermal storage concept. Many utilities will contribute cash rebates on the basis of "Avoided demand" for thermal storage systems.
Electric utilities generate power from several different energy sources with energy cost ranging from low cost hydro and nuclear to expensive gas turbines. Lower energy cost nuclear and hydro plants have excess capacity during off-peak hours (typically 9 pm to 9 am), while the cost of operating gas turbines for peaking often exceeds revenue from the power they generate. Lowering on-peak daytime demand and increasing off-peak nighttime demand enhances utility profitability. Load management just makes good economic sense. Cool thermal storage contributes to improved load management. The capital cost of cool thermal storage systems can be offset by utility savings passed on to the owner. The vehicle to pass on savings may be high daytime demand charges that are waived during off-peak hours, discounts for off-peak power or cash rebates for comfort systems that moves the power requirement from on-peak hours to off-peak hours.
A system of the present invention may serve as a dual purpose system for cool storage and water purification. It is particularly effective in treating dilute solutions. Polluted waters containing toxic pollutants in low concentrations are produced from various sources, such as underground waters, industrial waste waters and nuclear waste waters. Such waste water can be treated to produce usable water. A dual purpose system has tremendous advantages over conventional cool storage systems and conventional water purification systems.
2. Brief Description of the Prior Art
Since a dual purpose system of the present invention can provide both cool thermal storage and water purification, prior art on cool thermal storage and water purification by vacuum freezing are reviewed in the following:
2A. Cool Thermal Storage
Chilled water, ice or phase change materials can be used as a storage medium. Few phase change materials (other than water) have left the laboratory, and even fewer have met with any real success. For most comfort cooling applications, water is hard to beat as a storage medium. It is simply an economic question, "should water be cooled or frozen?"